<meta charset="utf-8">
(#) Negative Margins

!!! WARNING: Negative Margins
   This is a warning.

Id
:   `NegativeMargin`
Summary
:   Negative Margins
Note
:   **This issue is disabled by default**; use `--enable NegativeMargin`
Severity
:   Warning
Category
:   Usability
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   0.2.0 (October 2014)
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/NegativeMarginDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/NegativeMarginDetectorTest.kt)

Margin values should be positive. Negative values are generally a sign
that you are making assumptions about views surrounding the current one,
or may be tempted to turn off child clipping to allow a view to escape
its parent. Turning off child clipping to do this not only leads to poor
graphical performance, it also results in wrong touch event handling
since touch events are based strictly on a chain of parent-rect hit
tests. Finally, making assumptions about the size of strings can lead to
localization problems.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/negative_margins.xml:11:Warning: Margin values should not be
negative [NegativeMargin]
    &lt;TextView android:layout_marginTop="-1dp"/&gt; &lt;!-- WARNING --&gt;
              -------------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/negative_margins.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers

&lt;GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"&gt;

    &lt;TextView android:layout_margin="1dp"/&gt; &lt;!-- OK --&gt;
    &lt;TextView android:layout_marginLeft="1dp"/&gt; &lt;!-- OK --&gt;
    &lt;TextView android:layout_marginLeft="0dp"/&gt; &lt;!-- OK --&gt;
    &lt;TextView android:layout_marginTop="-1dp"/&gt; &lt;!-- WARNING --&gt;
    &lt;TextView android:layout_marginTop="@dimen/positive"/&gt; &lt;!-- OK --&gt;
    &lt;TextView android:layout_marginTop="@dimen/negative"/&gt; &lt;!-- WARNING --&gt;
    &lt;TextView android:paddingLeft="-1dp"/&gt; &lt;!-- OK --&gt;
    &lt;TextView android:layout_marginTop="-1dp" tools:ignore="NegativeMargin"/&gt; &lt;!-- SUPPRESSED --&gt;

&lt;/GridLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/NegativeMarginDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `NegativeMarginDetector.testLayoutWithoutRepositorySupport`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="NegativeMargin"` on
  the problematic XML element (or one of its enclosing elements). You
  may also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;resources xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;style layout_margin="..." tools:ignore="NegativeMargin" .../&gt;
    ...
  &lt;/resources&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="NegativeMargin" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'NegativeMargin'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore NegativeMargin ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

<!-- Markdeep: --><style class="fallback">body{visibility:hidden;white-space:pre;font-family:monospace}</style><script src="markdeep.min.js" charset="utf-8"></script><script src="https://morgan3d.github.io/markdeep/latest/markdeep.min.js" charset="utf-8"></script><script>window.alreadyProcessedMarkdeep||(document.body.style.visibility="visible")</script>